Field of the Invention
The invention relates to a method for operating a postpress system for producing and processing printed products, in particular for forming stacks or packs of product units which are preferably composed of a wrapping product and a plurality or collection of part products and/or inserts. The present invention additionally relates to postpress systems for performing the method.
Greater and greater demands are being made of postpress operations by the growth in localization and/or personalization of the editorial content of the products, but in particular advertising inserts. On the one hand, processing capacities need to be increased in order to improve profitability, and on the other hand it is also necessary to be able to faultlessly put together customized products in the correct sequence to make packs for distribution channels with as little manual intervention as possible, and make them ready for dispatch.
In the highly competitive advertising market, greater and greater demands are being made of the suppliers of print advertising and hence on the postpress process, and there is less and less tolerance of faults. In order to be able to maximize the profitability of advertising budgets, advertising customers are increasingly requiring that print advertising, i.e. primarily printed products but also product samples and data media, be delivered for specific customers or addressees. The more expensive the individual advertising medium, the greater the pressure to be able to specify the group of addressees.
For the postpress process, this means that customized printed products, i.e. ones compiled for specific addressees, need to be produced for a specific distribution channel faultlessly and additionally in the correct product sequence and to be processed to make up packs.
Because advertising customers only accept very low error rates (in the order of one-tenth of one percent), errors during the compilation of the products must be avoided or corrected at great effort and expense by hand.
Discussion of Related Art
Different methods are known from the prior art for ensuring that the products are compiled in the correct order or sequence in order to minimize the manual repair effort.
A method and a device for creating a product flow from a plurality of product units in a predefined sequence are thus, for example, proposed in WO 2013/159238, by means of which faulty product units of a sequence can be corrected without interrupting production and whilst maintaining the predefined sequence. In this method for creating a synchronized product flow of product units in a predefined sequence, in a first step products are fed to the grouping section of a first conveying device, and a synchronized product flow of product units is then created from the fed products along the grouping section in a predefined sequence, and the product units are transferred in the predefined sequence to a discharging device and discharged in a synchronized product flow.
If faults occur during the creation of the product units, they can be corrected subsequently by one or more faulty product units being rejected at a rejecting station. The rejecting causes a gap in the synchronized flow of product units which has a length of one or more cycles, depending on the number of faulty rejected product units. A new product unit is then created for each faulty product unit. It is, however, in particular proposed that, when only individual products are missing in the product unit, the incomplete product unit is fed onwards to the grouping section and completed. The missing or faulty products or product units are subsequently created correctly in the grouping section and then transferred to the discharging device. In order to insert this product unit subsequently at the correct position within this sequence, to reproduce the predefined product sequence, a bypass device is provided in WO 2013/159238 which makes it possible, by bypassing a conveying path section, to feed product units to the discharging device following the product gap timewise. In this way, the predefined sequence of product units from the discharging device is made available for further processing processes fully sorted and in order.
The length of the discharging device which is bypassed by the bypass unit must be at least long enough to allow a number of product units to be accommodated which is at least as great as the number of products between a gap and the newly produced or corrected product unit. The products are transported in the discharging device in a synchronized manner and evenly spaced apart from one another. For example, if 40 conveying devices for feeding products are arranged on the upper side of the grouping section, it has a minimum length of 40 cycles. Because the product collections are held and transported along the lower side to an output point for transfer to the discharging device after they have passed through the upper side, the length increases to at least 80 cycles, i.e. the bypassed length of the discharging section must be at least 80 cycles long in order to be able to hold the whole quantity of product units between the gap and the corrected or newly produced product unit. In practice, the section will be significantly greater because of the lower number of feed units at the grouping section.
One of the main sources of faults in the production of product units, preferably printed end products such as collections of main and/or part products, inserts, leaflets, cards and the like, is the supply of the abovementioned products. Thus, for example, leaflets with poor paper quality often cause faults in the feed device, which result in it not being possible for these products to be correctly added to the collections or product units to be created. However, the same problem also occurs with very high-value products with coatings, of products made from a smooth film material which, on the one hand, are hard to grip and, on the other hand, often stick to one another with an electrostatic charge.
Because postpress businesses are subject to greater and greater pressure on quality, there is also a need to further reduce error rates in the production of route adapted packaged product flows, and at the same time to optimize use of the existing system capacity, in particular the stacking device capacity too.